Despite continuing advances in imaging technology, plain (projection) x-ray radiographs remain a staple diagnostic technology within the world of medicine. While magnetic resonance imaging (MRI) and computer tomography scans (CT scans) can reveal a wider range of tissue structures and better resolve spatial relationships, e.g. through three-dimensional or cross-sectional images, the relatively low cost, wide availability, and simplicity of plain radiographs make them the imaging technique of choice whenever possible.
In particular, plain radiographs remain in wide use in the field of dentistry. To obtain a radiograph, a dental technician positions an x-ray source and an image receptor on either side of the portion of the patient's palate to be imaged. Often, the image receptor is positioned intraorally, and is held in place against the patient's palate by the biting action of the patient on a bite plate or bite stick. For film-screen plain radiographs, the image receptor comprises an unexposed sheet of film that is exposed by incident x-ray radiation. For digital plain radiographs, which are becoming increasingly common, the image receptor comprises a sensor plate that converts incident x-ray radiation into digital information. In either case, the x-rays emitted from the x-ray source are partially blocked by dense tissues such as bone. The patient's teeth thus cast “shadows” on the image receptor. In the resulting image, either a developed film image or a digital image, bone structures appear as lighter regions among darker regions of softer tissue.
FIG. 1 shows an exemplary conventional dental x-ray machine 10, which typically comprises a base 12, an articulated extension arm 16, and a tubehead 20 housing an x-ray source. The base 12 anchors the x-ray machine 10 to the floor FLR of dental facility, and is typically accompanied by a control panel 26 with which a dental technician can adjust the radiograph parameters, and initiate image acquisition. In many instances, the control panel 26, or a second, auxiliary control panel, is removed from the base 12, e.g. outside the patient room, allowing the dental technician to initiate image acquisition from a location with reduced radiation exposure. The articulated extension arm 16 extends outward from the base 12 and supports the tubehead 20, allowing the tubehead 20 to be easily positioned and oriented as needed. The tubehead 20 typically comprises a heavy, e.g. lead, metal housing 22 that encloses the x-ray source, such as a hot cathode, i.e. Coolidge, x-ray tube.
The x-rays emitted by the x-ray tube emerge from the metal housing 22 through a lead collimator that partially collimates the x-ray beam. A tubehead seal, such as comprising a thin aluminum sheet, spans the lead collimator, to filter the long wavelength, low energy, i.e. soft, x-rays emitted by the x-ray tube and “harden” the x-ray beam 32. Soft x-rays do not effectively penetrate biological tissues but are instead absorbed. While soft x-rays are not useful for imaging, they remain potentially harmful, and are therefore typically filtered.
A position indicating device 24, typically comprising a lead-lined cylinder, extends outwards from the metal housing 22, coaxial with the x-ray beam, to further collimate the x-ray beam and assist the dental technician in aiming the x-ray beam.
Obtaining quality radiographs of patient's teeth is an important function of any dental technician. Indeed, poor quality radiographs, i.e. radiographs with poor resolution, makes detection of many adverse dental conditions, e.g. small, incipient fractures within a tooth, difficult or impossible. Relative motion of the tubehead 20, palate, and image receptor can lead to blurred features within a resulting radiograph. Accordingly, a dental technician will often instruct a patient to “Hold still!”, while the technician exits the room and activates the x-ray tube to expose the radiograph.
Movement of the tubehead 20 is often detrimental to the quality of the exposed image. Despite the relatively rigid construction of the extension arm 16, the tubehead 20 often is exhibits substantial oscillatory movement after a dental technician positions it. The motion can persist while the dental technician exits the room to activate the x-ray tube, significantly compromising image quality. The partially collimated nature of the x-ray beam and, in the case of intraoral radiographs, the relatively small spatial separation between the palate and the image receptor mitigate the effects of such relative motion. Nonetheless, motion of the tubehead 20 can potentially degrade the quality of radiograph.
It would thus be advantageous to provide a structure, system, and/or process by which activation of an x-ray system is allowed to proceed under conditions wherein relative movement between a tubehead and the image receptor is acceptable. Such a structure, system, and/or process would provide a substantial technical advance.
Furthermore, it would be advantageous to provide a structure, system and/or process for preventing activation of an x-ray source if relative movement between a tubehead and the image receptor would otherwise result in poor quality x-ray images. Such a structure, system, and/or process would provide an additional technical advance.